A tire comprising a novel type of anchoring of its carcass reinforcement in its beads was proposed in publication WO 98/54006. According to this document, this tire comprises a crown reinforced by a crown reinforcement, two beads and two sidewalls connecting the crown to the beads. This tire comprises a carcass reinforcement with first reinforcing threads arranged adjacent in the circumferential direction, each of said first reinforcing threads forming in the sidewalls a zero or low angle with the meridian direction from each bead to the crown. This carcass reinforcement is anchored within each bead to an anchoring structure comprising at least one second reinforcement oriented circumferentially and cooperating with an adjacent portion of the carcass reinforcement by means of an anchoring rubber mix. This anchoring rubber mix is such that its elasticity modulus for a deformation of 10% is greater than 20 MPa and preferably greater than 30 MPa.
This novel structure of the tire beads yields excellent results in particular in terms of endurance, that is to say good resistance to mechanical stresses over time. It has however been noted that the high rigidity of these beads, due, inter alia, to the presence of the second reinforcement and of the anchoring mix of high elasticity modulus greater than 20 MPa, could be the cause of difficulties in mounting and/or demounting a tire on/from its mounting wheel, in particular in the case of manual mounting and/or demounting operations. This problem is particularly significant for tires intended for passenger vehicles, these tires having low section heights and comprising very rigid anchoring structures. “Section height of a tire measured when the latter is mounted on its mounting rim” is understood to mean the height of said section of the tire viewed in meridian section (that is to say in an axial plane containing the axis of rotation) and measured between the mounting rim seat and the radially outermost part of the crown of the tire. “Relatively low section height” is understood in the present specification to mean a section height of less than 86 mm.
This problem is even more pronounced if the mounting rim comprises a rim seat which is extended axially towards the inside by a protrusion of low height (alternatively referred to as “hump”) intended to hold the bead of the tire on its seat in the event of partial or total deflation of the tire. The presence of this protrusion or hump causes real difficulties when mounting a tire such as described above, and these difficulties may furthermore result in incorrect placement of the beads on the rim seats.
The objective of the present invention is to overcome this problem.